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Subject[14/17] Add VM_BUG_ONs to check for correct page order
Before we start changing the page order we better get some debugging
in there that trips us up whenever a wrong order page shows up in a
mapping. This will be helpful for converting new filesystems to
utilize higher orders.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

---
mm/filemap.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
Index: linux-2.6.21-rc7/mm/filemap.c
===================================================================
--- linux-2.6.21-rc7.orig/mm/filemap.c 2007-04-24 11:45:26.000000000 -0700
+++ linux-2.6.21-rc7/mm/filemap.c 2007-04-24 11:46:04.000000000 -0700
@@ -127,6 +127,7 @@ void remove_from_page_cache(struct page
struct address_space *mapping = page->mapping;

BUG_ON(!PageLocked(page));
+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));

write_lock_irq(&mapping->tree_lock);
__remove_from_page_cache(page);
@@ -268,6 +269,7 @@ int wait_on_page_writeback_range(struct
if (page->index > end)
continue;

+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));
wait_on_page_writeback(page);
if (PageError(page))
ret = -EIO;
@@ -439,6 +441,7 @@ int add_to_page_cache(struct page *page,
{
int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);

+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));
if (error == 0) {
write_lock_irq(&mapping->tree_lock);
error = radix_tree_insert(&mapping->page_tree, offset, page);
@@ -598,8 +601,10 @@ struct page * find_get_page(struct addre

read_lock_irq(&mapping->tree_lock);
page = radix_tree_lookup(&mapping->page_tree, offset);
- if (page)
+ if (page) {
+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));
page_cache_get(page);
+ }
read_unlock_irq(&mapping->tree_lock);
return page;
}
@@ -624,6 +629,7 @@ struct page *find_lock_page(struct addre
repeat:
page = radix_tree_lookup(&mapping->page_tree, offset);
if (page) {
+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));
page_cache_get(page);
if (TestSetPageLocked(page)) {
read_unlock_irq(&mapping->tree_lock);
@@ -685,6 +691,7 @@ repeat:
} else if (err == -EEXIST)
goto repeat;
}
+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));
if (cached_page)
page_cache_release(cached_page);
return page;
@@ -716,8 +723,10 @@ unsigned find_get_pages(struct address_s
read_lock_irq(&mapping->tree_lock);
ret = radix_tree_gang_lookup(&mapping->page_tree,
(void **)pages, start, nr_pages);
- for (i = 0; i < ret; i++)
+ for (i = 0; i < ret; i++) {
+ VM_BUG_ON(mapping_order(mapping) != compound_order(pages[i]));
page_cache_get(pages[i]);
+ }
read_unlock_irq(&mapping->tree_lock);
return ret;
}
@@ -747,6 +756,7 @@ unsigned find_get_pages_contig(struct ad
if (pages[i]->mapping == NULL || pages[i]->index != index)
break;

+ VM_BUG_ON(mapping_order(mapping) != compound_order(pages[i]));
page_cache_get(pages[i]);
index++;
}
@@ -774,8 +784,10 @@ unsigned find_get_pages_tag(struct addre
read_lock_irq(&mapping->tree_lock);
ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
(void **)pages, *index, nr_pages, tag);
- for (i = 0; i < ret; i++)
+ for (i = 0; i < ret; i++) {
+ VM_BUG_ON(mapping_order(mapping) != compound_order(pages[i]));
page_cache_get(pages[i]);
+ }
if (ret)
*index = pages[ret - 1]->index + 1;
read_unlock_irq(&mapping->tree_lock);
@@ -2457,6 +2469,7 @@ int try_to_release_page(struct page *pag
struct address_space * const mapping = page->mapping;

BUG_ON(!PageLocked(page));
+ VM_BUG_ON(mapping_order(mapping) != compound_order(page));
if (PageWriteback(page))
return 0;

--
-
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